bark beetles – Enviro Updates

Jane Braxton Little, HIGH COUNTRY NEWS

…at the heart of the logging debate is the question of whether dead trees are a fire hazard. The conventional assumption is that insect outbreaks increase wildfire risk because dead trees are more flammable than green ones. That is a conclusion most scientists have long disputed.

Looking north from Blue Canyon near Shaver Lake, copper-colored forests blanket mountain slopes that stretch ridge after ridge to the horizon. The patches of fading green that dappled these hillsides last fall have merged into an unbroken cover of rust-needled pines. At dusk, when the winds die down, an eerie stillness gives way to the muffled sound of munching as beetles chomp through one tree after another, thousands after thousands.

This is the look — and the sound — of drought.

Four consecutive winters with little to no snowpack, followed by four dry summers, have devastated California’s southern Sierra Nevada. At least 66 million trees are already dead statewide, and millions more are expected to die as the drought persists into a fifth summer.

On the Sierra National Forest, up to 90 percent of the mid-elevation ponderosa pines are dead. Weakened by drought, oaks are succumbing to sudden oak death along the central and northern coast, and the disease has moved into the Central Valley. Pines gray as ghosts haunt coastal, Cascade and Sierra foothills. The epidemic is spreading across choice vistas owned by millionaires as well as remote landscapes rarely entered by humans.

And the bark beetles that caused this desolation? They’re reproducing at triple the normal rate. Forest ecologists used to consider them a natural part of the forest dynamic — and they are. Stressed by drought and decades of air pollution in overcrowded stands, however, the natural chemicals trees pitch out in self-defense can’t keep up with the onslaught of bugs. No one is calling what’s happening here natural anymore.

“Nobody imagined this would come on as fast as it has, or be as lethal,” says Craig Thomas, conservation director for Sierra Forest Legacy, a coalition focused on Sierra Nevada national forest issues. “And nobody really knows what the hell to do.”

Overwhelmed by the die-off, forest management agencies are resorting to a century-old strategy: removing dead trees to minimize future wildfires, which they predict will be inevitable and cataclysmic. Gov. Jerry Brown declared a state of emergency in October, citing a public safety hazard from falling trees and worsening wildfire risks. The tree mortality task force he convened has marshaled a small army to log over 6 million acres.

Soumya Karlamanla, LOS ANGELES TIMES
Call it a vicious cycle: drought, wildfires and bark beetles.
California’s historic drought stresses trees across the state, making them ideal prey for bark beetles. The insect infestations dry out vegetation further, creating forests that can light up like tinder. Fires then damage more trees, attracting more beetles, and turning more forests brown.
“So we all have to hope for rain,” said Tom Smith, park pest management specialist for the Central and Southern Sierra Region for the California Department of Forestry and Fire Protection.

Bark beetles probably exacerbated the fire that ravaged Lake County over the weekend, he said. Experts called the Valley fire’s rapid spread unprecedented; the blaze, which began Saturday afternoon, grew to more than 40,000 acres in fewer than 12 hours.
“This last couple years has just been so extreme that everything’s under stress,” Smith said. “If we weren’t in the drought, we wouldn’t have so much bark beetle.”
He said there’s been heavy beetle activity in Lake County, and around Clear Lake, where the Valley fire is blazing. A U.S. Forest Service survey of the region in and around the Bay Area in June found that though tree mortality was increasing almost everywhere, the worst region by far was an area south of the lake.
UC Berkeley fire science professor Scott L. Stephens agreed that bark beetles in the area likely left dead trees ready to go up in flames. “There’s no doubt that’s going to enhance a fire,” he said.
He said that dead pine trees are much easier to catch on fire when they still have their needles, and they don’t lose them until a year after beetles kill them. Though pines that have been dead for years aren’t quick to ignite, the recently killed ones are standing fuel, he said.
Read more at: Meet the insect that helped fuel Northern California’s Valley fire destruction – LA Times

Environmental Center of Sonoma County

Tag: bark beetles

California plans to log its drought-killed trees: may not reduce fire risk

Meet the insect that helped fuel the Valley fire destruction